1. Field of the Invention
The present invention concerns bacterial autoinducers of growth, methods for their purification. autoinducers purified by such methods, and their use to induce the growth of bacteria, both the source organism and other species.
2. Description of the Related Art
Signalling events between bacteria and host cells are an integral component of the dynamic and complex process of infection and disease. It has recently become clear that signalling between bacteria is also of importance to this process.
Lows molecular weight, diffusible signal molecules produced by bacteria, termed autoinducers (AI), play a crucial role in the development of bacterial infections, of both plants and animals. These autoinducers may determine whether or not an initial infection, often involving only a very few bacteria, will succumb to the many defence mechanisms of a host or whether these host defences are overcome, and bacterial growth and disease occur.
One class of autoinducers has already been well-characterised, the N-acyl homoserine lactones, which are composed of derivatives of amino acid and fatty acid molecules. This family of molecules play a key role in the mechanisms by which Gram negative bacteria monitor population densities, factors which are important in virulence of a number species. However, despite the fact that N-acyl homoserine lactone-type sensing systems have been shown to exist in E. Coli, there is so far no evidence that N-acyl homoserine lactones themselves are made by, or play a role in the pathogenesis of this organism. In addition, no evidence has been so far been presented to suggest a role for these autoinducers in the pathogenensis of Salmonella.
The existence of an additional class of autoinducer molecule has been shown the AI being different from the homoserine lactones. These also appear to play an important role in pathogenesis.
A purported bacterial AI was isolated by Lyte, M. et al. (1996, FEMS Microbiology Letters, 139: 155-159) having a molecular weight of approximately 10,000 Da (see also, byte, M., 1993 Journal of Endocrinology, 137: 343-345: U.S. Pat. No. 5,629,349).